In vehicles, aircraft, telecommunications and other systems, it is necessary to monitor and control electrical power delivered to various loads. Also, it is desirable to identify an open load state at an output port that is adapted to deliver electrical power to a load. An open load state at an output port may, for example, indicate a malfunction (e.g., a defective LED) or a missing circuit (e.g., a broken connector, wire or load) at the output port. The detected open load condition may represent the absence of a load or may represent a current reduction as measured when a single load or lamp in a multiple load circuit is open.
Production trailer tow designs consist of a mechanical connector with switching and fixed protection devices distributed in one or more modules within the vehicle. In this trailer tow design it is possible for a trailer with a known open load condition to be connected to a tow vehicle without detection of the open load condition. This may lead to hazardous situations where a trailer with non-functioning exterior lights can be pulled by a tow vehicle with no direct detection or indication of the malfunctioning trailer lights. Additionally, partial open detection (e.g., one or more loads open in a multiple load circuit) is also not available. An example would be the marker or running lamp circuit on a travel trailer, which may have eight or more side amber markers (secondary lamps) and two rear marker lamps (primary). The rear marker lamps could be open while the side markers were functioning properly as viewed in the rear view mirror of the tow vehicle. This would not provide a visual indication to the driver that there was a problem, while from the rear the trailer would not be visible to approaching vehicles.
In vehicles designed to tow trailers, a trailer tow connector and electrical components installed in the vehicle to control trailer loads, are typically used to deliver electrical power to the trailer and also to monitor and control various devices or loads installed in the trailer. The trailer tow connector generally includes one or more output ports or pins adapted to deliver electrical power to the trailer devices or loads. The devices may include running lights, brake lights, parking lights, electric brakes, trailer battery and turn signals. Selected output ports or pins in the trailer tow connector are usually connected to a device that serves a particular purpose. For example, there may be an output port for operating the brake lights on the trailer and another output port for operating the right-hand turn signal and yet another for operating the left-hand turn signal.
Existing trailer tow connectors and the electrical components installed in the vehicle to control trailer loads typically lack the capability to perform real time measurement of load currents and to intelligently set open circuit current limits based on the measurements. Simple open detection, as connecting a trailer with a pre-existing open such as a burned out bulb, can not be detected and annunciated to the driver. Furthermore, a vehicle may be used to tow several types and sizes of trailers that have different electrical loads further complicating open load detection in a multiple load circuit, such as trailer marker or running lamps. Existing trailer tow connectors with their supporting electronic switching and fixed protection devices lack the capability to set open circuit current limits based on the load characteristics and observed conditions. Also, existing trailer tow connectors lack the capability to identify an unbalanced load condition in a symmetric load configuration if a pre-existing open is present prior to the connection of the trailer.